


Demonic Intervention

by IruMinO



Category: Ao no Exorcist | Blue Exorcist, Kuroshitsuji | Black Butler
Genre: Gen, Other Additional Tags to Be Added, Rating May Change, character tags will be added as they appear
Language: English
Status: In-Progress
Published: 2020-01-14
Updated: 2020-01-14
Packaged: 2021-02-26 07:04:48
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,877
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22251421
Author URL: https://archiveofourown.org/users/IruMinO/pseuds/IruMinO
Summary: Okumura Rin, 15 years old, when he is about to make his debut as a respectable True Cross Academy Culinary Department student, a tragic incident happens,An incident which reveals a whole new world he’s oblivious about.First, demons are real, and his biological father is one. Second, his little brother has been keeping secrets since they’re seven, and he intends to know every single one of them. Third, a demon is taking over his life and actively preventing him from getting his usual 11 hours sleep.He is very much not equipped to deal with this demonic mess.
Relationships: Okumura Rin & Okumura Yukio, Sebastian Michaelis & Okumura Yukio
Comments: 2
Kudos: 39





	1. That Demon, Savior

As long as Rin remember, the Crow has been following his little brother since they’re eleven. That day Yukio came back to the monastery with a big black bird perched on his brother’s hat covered head. His little brother explained that the bird was attached to him because he freed it from a trap. Rin didn’t think much of it, at the time; he was simply amazed and happy for his brother, and a little bit envious because father permitted the bird to stay; unlike their many attempts at bringing tiny critters to be raised as pets before. Yukio named the bird Sebastian.

In retrospect, he should have found it suspicious, because a bird like that didn’t just follow a human everywhere unless it was raised since it was very young, on top of that, the bird was too smart to be a simple crow. If he had inkling that the bird was more than it let on, he might be able to overcome his shock when the bird transforms into a human and promptly drags him out of the monastery, leaving his formerly possessed father to sacrifice himself closing the Gehenna Gate.

“LET ME GO YOU DAMN BIRD!! We have to help my father!!” Rin screams, struggling mightily from the bird-turned-human’s hold.

The demon, because the bird is a fucking demon, of course, makes a noise of clear disapproval. “It would not be wise to do so Little Prince—”

“Don’t call me that!! I have to save him!!” Rin cuts him off, struggle renews at the nickname, because that title reminds him again what started this whole disaster.

Sebastian continues, ignoring the interruption, “Your adoptive father has summoned the strongest entity under his contract to close the Gehenna Gate, and it will likely cost him his life. If you come back there, all of Reverend Fujimoto sacrificed would be in vain, because while your father is dying, Satan could and would send one of his strongest underlings, probably one of your brothers, to finish the job of returning your princely behind to Gehenna.”

Rin struggles weakly, still can’t accept Sebastian’s words, but doesn’t know how to refute him. If his brother is here he would know how to convince—wait, Yukio, “Where is Yukio?!!” the half demon’s panic turns into a new direction.

“We are going to meet Master Yukio actually; he’s on his way to your little café,” the demon smiles, Rin despairs.

Suddenly, the implication that he is been lied to for all his life hit him, and he stops struggling.

“Why did they lie to me, Sebastian?” Rin asks quietly, his head down.

“Even I was surprised that you’re a son of the God of Gehenna. Your brother has this annoying habit of keeping everything to himself, he sure knows how to keep a secret,” Sebastian answers, a little bit perturbed but there is a hint of admiration in that sentence.

Rin laughs, it tastes a little bitter, “Yeah, that moley four eyes, what an awful little brother,” as he says that, abruptly tears pour uncontrollably out of his eyes along with wracking sobs that staggers the usually unshakable teen.

“My, my, we can’t have you crying your heart out here, now can we?” Sebastian then picked up the teen into his arm then takes off to the roof, ignoring the Little Prince muffled protest of his treatment, “Hush now Little Prince, the sooner you meet Master Yukio the better, you’re not out of danger yet.”

Rin doesn’t reply, he only has Yukio now, since that shitty old priest is gone and done it--in the most heroic way, yes, but that doesn’t change the fact that he and his brother no longer has a father, _he only has Yukio now_, god, how is he going to protect his little brother from now on?...

His tears don’t get a chance to begin anew as they’ve arrived at the yet unopened café. Rin almost smiles, the café was Yukio’s idea.

* * *

_“Nii-san maybe the reason you cannot keep a job is because they, in many shape and form, are _orders_? We both know you can’t follow the simplest ones,” Yukio smiled at him in that infuriating way that Rin wanted to hit him._

_“What’s that supposed to mean Four Eyes?!” Rin asked, very much irritated._

_“Maybe if you’re your own boss…like opening your own restaurant or café or something…” Yukio tried to explain, but before he finish Rin all of suddenly straightened his posture and enthusiastically remarked, “That would be awesome!! I do know how to cook and baking can’t be that hard if I have the recipe and utensils; and I can hire pretty girls to be waitresses,” but then he deflated, “But I don’t have that kind of money to start…”_

_Yukio was silent for a while, “We don’t need to start from scratch. I’ll talk to father, he might know someone,” his little brother smiled._

_The next day, the Old Man sat him down, brandished few shiny looking papers, and introduced him to Mr. Tanaka that will guide him in his journey of owning a little café; the elderly man frankly told him that he wished Rin to run his family café since he has no children to speak of and his employees are mostly undergraduate students who moved on after they graduate. But before that, Rin has to go to Culinary School and learn the way of Food, so that Mr. Tanaka can be at peace when he finally gives Rin the reins. The paper was a brochure from True Cross Academy: Culinary Department and so Rin has to pass the entrance exam in three months._

* * *

That was five months ago, he was ready to move to True Cross academy with his brother tomorrow, study with all his might and finally to make a respectable reputation for himself, without the ‘demon child’ infamy to color his peers opinion of him. However, now everything’s going to change, because apparently he’s literally a demon-spawn, ironically proving those people were right whenever they call him ‘demon child’.

Rin's hold on Sebastian dress jacket tightens, 'Yukio is the master of this demon...?'

Rin glares at the bird-turned-humanoid above him and concludes that his brother is not normal in every stretch, and it has been that way for a long time, evidently.

He really needs to have that long overdue talk with his <strike>awful</strike> beloved little brother.


	2. That Demon, Caring (?)

**Summary for the Chapter:**

> A little flashback from Yukio's side of things before we're back to the current events.

**Notes for the Chapter:**

> Two chapter immediately because I've made some people wait too long already. Enjoy!

Yukio entered the Abbey to hear the tail end of an argument between Father and his twin brother. Earlier, Rin was on an errand from Father, but judging by his brother’s appearance, he got into another fight. Yukio repressed a sigh.

“You think I didn’t know that?? I know that they can take back my admittance into their fancy cooking school, but what those assholes did sicken me! I can’t just stand there and do nothing!!”

Yukio didn’t miss the wild flame that flashed blue for a brief second as the heater exploded, as if responding to his brother’s outburst.

“You’re grounded until you have to move tomorrow,” Father decided, “and tonight lights out at 8, no buts! This is a punishment! You’re not supposed to like it! Unless, of course you’re much older, and you and your partner are both into such things! Consent must be mutual after all,” Father ended his tirade with a grin so inappropriate in the face of a supposedly holy man that Yukio had to cover his face briefly to hide his second hand embarrassment. His face had nothing on his brother’s though. His twin’s face was redder than a boiled octopus and Yukio briefly saw smokes coming up of his brother’s head and ears.

“S-SHUT UP, YOU DIRTY OLD PRIEST!!” Rin shrieked, arms and legs flailing as he expressed his inner mortification and the heater makes a comeback with another bluish explosion. That was really concerning—but really, his twin probably remembered The Talk they had the previous year, it was as embarrassing as it was mortifying, an eye opening revelation about their father’s youth, and definitely something he didn’t want to remember, _yet_. So, Yukio took a deep calming breath, thought serene thoughts and cold hard facts, and gradually his blush disappeared.

Yukio tried to catch his Father’s eye and his father met his eyes in a meaningful way, then Yukio understood. Fujimoto Shiro didn’t say those things just to embarrass his older brother; the Paladin was gauging the Seal’s deterioration effect on his brother. Now, they both can conclude that any strong emotion, whether anger or embarrassment, was enough to let his brother’s flame to slip through the cracks.

‘Ah, the timing couldn’t be worse,’ Yukio thought as he bandages his brother’s scraped hands. They both would be moving to The True Cross Academy Dormitory tomorrow. If anything happen before that, his brother will begin his career as a Cooking Department student as a demon.

It was a good thing that his brother was grounded until then, hopefully he won’t get into trouble.

But, Yukio rarely hope. He knew for a fact that his kindly but impulsive brother never starts any of his fight, the fights always find him.

* * *

Yukio just never think that the fight would come that very night in the form a lilac haired teenager possessed by Astaroth. Worse, he is currently away from the Abbey, reporting the happening of that afternoon to his current supervisor, Mephisto Pheles, the Head of True Cross Order Japanese Branch, in person. Yukio knows that Father has called Sir Pheles directly after, but the Baal still insists that Yukio comes to report. The young exorcist tries to refuse, he has a bad feeling about this but seems like Fahter Fujimoto realizes something he doesn’t because he convinces Yukio to go, but if it will make him feels better, Yukio can leave Sebastian in his command while he’s gone. So, the crow remains in the abbey.

His familiar texts him the situation, confirming his gut feeling that his decision to obey the King of Time is a very bad call. Yukio sends the eccentric principal a venomous glare, he’s very sure that this arrangement was not a coincidence in the least. Being the King of Time, Yukio vaguely knows that Sir Pheles is able to see into time; past, present, _future_. Thus, there must be a reason why he’s in this situation; separated from his father and brother, and practically hidden in the bowels of this gigantic gaudy mansion, behind the strongest wards in the entirety of Japan.

“Why?” he frowns at the moe-moe yukata clad headmaster, ignoring the Baals’s distracting appearance.

Mephisto smirks, his eyes twinkling with an appreciation for this child that has mind sharper than most adults he’s acquaintance with, an exceedingly decorated child exorcist that knows his place in the face of an apex predator but still rebellious enough to question _him_, someone so far up in the power chart the child can’t hope to match him in a million years (_if he stays human, that is_). Well, Mephisto supposed the boy has earned himself a little reward for his composure. Any other child would have tried to bust his window by now, after realizing that the door is locked. So the Baal, put down his treasured manga and face the boy properly.

“Because you’re weak,” his tone taunting, receiving a glare so concentrated that briefly makes him wonder if he’s suddenly on fire, unperturbed, Mephisto smiles, showing his sharp incisors, and continues, “While your rank as an exorcist is very much a noteworthy record in the history of True Cross Order and I know you can handle a little army of the Rot family, you wouldn’t be able to handle what comes after.”

Yukio only need to think for a brief second before his expression turns horrified, “Satan,” he out loud whispers.

“Yes, this is inevitable, trust me,” _‘I am the King of Time’_ goes unsaid.

“What about my brother’s fate?”

“Oh?” Mephisto suddenly looks very interested, “Do you believe in fate now, little exorcist?”

“Fate is ever changing.”

“Yes, you humans have the power to alter reality to a completely new direction, always so fascinating,” the demon muses out loud. “But to answer your question, I don’t know,” Mephisto says simply.

Yukio is taken a back. “You…don’t know?” he asks, rather unbelieving.

“It happens sometimes,” the pink yukata clad demon says cheerily, almost mocking, whether directed towards Mephisto himself or the boy sitting in the plush chair in front of his desk is debatable, “tonight is a night saturated by the hands of fates; it can go into either way.”

“So there is a chance that my brother does not become a demon tonight,” Yukio says, relief tinting his calculating tone.

The purple haired demon seems to be contemplating something before responding, he stands up from his comfortable chair to stand in front of his desk, facing the seated boy directly. The tall demon then bends down so the young exorcist doesn’t have a choice but to look him in the eyes. Mephisto smirks, he reaches out a hand behind Yukio’s neck and bring their faces together, a small laugh escaped the demon’s lips as he notice the suddenly frozen stiff state of his guest, ‘Heh, let this be a lesson too,’ Mephisto thinks, his smirk’s widening into a combination of playful and sinister grin.

“Okumura-kun, I’ll share a secret with you tonight,” his voice turns darkly entrancing. Repressing another giggle at the shudder that runs through the Paladin’s protégé young inexperienced body, Mephisto continues, “Let’s just say, no one will have any say on Okumura Rin’s transformation if you don’t have _that_ powerful familiar at your beck and call. That demon, was and still is fate’s greatest meddler,” the headmaster concludes and finally putting back their distance into a more appropriate and manageable space.

Yukio has too looks up, the boy's expression is giving the demon a sudden urge to bring out his camera and capture that blushing but annoyed face; in any other context, that expression is a textbook tsundere face. What an adorable sight—no wonder this boy’s fans become rather fanatic lately. Mephisto let out another amused laugh, whips up his phone out of his pocket and the sound of camera shutters fills the air.

“Please delete it, Sir Pheles,” Yukio asks with gritted teeth, almost losing his hard trained composure at the noise.

The supposedly dignified Honorary Knight of True Cross order gleefully tells him, “No.”

Yukio sighs, that protest is just a token of effort, since he already knows that the strange demon will not heed his request. Not even the Grigori has complete control of the demon king in front of him, what chance does he has—high ranked exorcist or no, no one orders the Baal and expect him follows it (unless it’s to his advantages of course). Yukio takes a rather long breath, inside lamenting that the damn picture will join the collection of his embarrassing and unsightly photos taken through the years he’s acquaintance with the oddball of a headmaster. Gods, even Shura-san is not this bad when teasing him, he just hopes neither Shura or his twin ever find the damn album…

The thought about his brother brings him back into his current predicament and Sir Pheles’s latest words, now he’s mostly certain that his brother will survive the night with his humanity intact. He also takes a mental note to put another fact in Sebastian file inside his head, _‘Fates’ greatest meddler…’_ by description alone it sounds like his familiar has done things that derails a lot of things from their fixed tracks. What kind demon is that? Yukio has thought that if there is such chaos bringer demon, it would be the purple haired demon in front of him. However, with this bit of information Yukio once again concludes that he doesn’t know demons as well as he thought. And it seems like after meeting Sebastian, his exorcist education about demonology become less and less certain; it becomes more and more questionable.

Yukio’s worries shift to Father Fujimoto, “What about the Paladin?”

Mephisto hums, not bothered at all by the urgency in the boy’s voice, “His chance of survival plummet as your beloved twin’s survival chance arise. Either way, you’re losing something tonight. Whether it’s your brother’s humanity or your father’s steadfast presence has yet to be decided. Now, eat your dinner,” the headmaster orders as pink smokes suddenly appear camouflaging the magic at works conjuring the limited edition of a ramen cup noodles. Yukio stares at the ramen then at the headmaster then at the rest of the conjured junk food on top of the principal desk.

“Why are you like this? I thought Father _is_ your friend, don’t you care at all whether he survive the night or not?”

The principal expression changes into an amused stare, “That is such interesting notion; a demon caring for a human’s survival, a man’s life is always so short from my perspective, little one,” the Baal returns to his seat behind the desk, ungloved hands reaching for a golden edition of another famous ramen, his bared claws looks as intimidating as the grin the headmaster currently support on his face, “Fufufufuhahahaha…well, I supposed I am as fond as I am capable of your adoptive father. But that doesn’t mean I plan to bet this body against my dear old father, there is a reason I survive this long,” he pauses to pour a hot water into his cup, close the lid and set a timer, and then the demon set aside his meal to put his attention fully onto the boy exorcist. “And that is I don’t recklessly risk my health for such as selfish notion of saving a ‘friend’ who will probably reach his natural death in a few years. There are a lot more important things at stake than the life of a single mortal.”

“Even though you love him …”

“A demon doesn’t— ” then his something beeps, Yukio thought that it is the timer for the ramen but he’s wrong, Mephisto suddenly stands up, and stare at Yukio with an unnerving gaze, “It’s done, it’s best that you meet your brother now and secure him behind a strong ward. You have a lot of things you need to explain to your other half, Okumura-kun. I suggest you go now before your beloved brother has another break down,” the menacing grin is back and Yukio doesn’t waste any more time to get out of his too plush chair, heading out of the door, then take off sprinting the moment he’s out of the headmaster opulent office.

As he run, he sent orders to Sebastian to bring his brother to agreed discussed location. After that his attention is focused into where he’s going. Yukio is surprised that the sky is already so dark.

Damn it when did that demon use his power on him?! that is the only explanation, because he only have the memory of barely 30 minutes with the headmaster, what happen in the last three hours? Did the King of Time freeze him in time or did he fast forward the pace of time around him. He really doesn’t have any idea on how the Baal’s power works. And it’s not like he can test the theories he has. Because other than the flair of dramatics conjuration and appearance/disappearance, the magic keys, and his small dog transformation, he has never seen the demon use his power. Really, Mephisto Pheles might have been with the human side for two hundred years but Yukio doesn’t think that many really know the demon’s true power.

His thoughts on the King of Time is screeching to halt the moment he recognize the neighborhood, he’s on the Northern True Cross District, just a few blocks from the little café, his destination. He turns into an alley that would lead to a short cut, ignoring the people he passes, he might seems rude but he has a brother to look after and probably a father to be buried. Yukio expertly ignore the sting of tears that threatens to spill from his eyelids.

_‘Damnit Mephisto!’ _damn that clown for preventing Yukio to be there by his father side, protecting his twin, why does he has to be so damn weak. He’s always, always not good enough, not strong enough, not fast enough, not powerful enough…he is never enough when it counts.

The gathered tears now clouding his sight and he almost lose his footing but he catches himself in time. He finds his brother hunched form before the back door of the café. Sebastian’s tall figure stands almost standoffish to the side, the demon would look emotionless if not for the slight furrows between his eyebrows.

“Nii-san.”

His brother seems startled; he slowly stands, and even slower turns around, “Yukio…”

Yukio observes his twin minutely, noting the still rounded ears, taking in that there are no fangs peeking out of his brother’s dry lips, also noticing that there is no tail lagging behind his brother’s back, and finally his puffy red eyes on a face so devastated Yukio can’t hold his own tears anymore—Rin still looks human—their father is dead.

Father is dead. His brother never cried. Nothing else would cause his brother’s sorrowful face.

Father is dead.

Father … is …

Dead…

The tears spill without his permission and suddenly he has an armful of an older twin brother. He embraces Rin with all his strength, knows that Rin can take it, trying to convey his despair through it. Rin’s embrace is suffocating but it’s also smothering his sharp pained sobs. He can feel his brother’s tears seeping through his clothes, reaching his skin, and the vibration of his twin’s whimpers.

They will probably stay in each other desperate embrace for a long time if not for Sebastian gently herd them inside the building. They don’t get the chance to talk as both fell asleep in exhaustion the moment their body hit a mattress.

The demon put a thick blanket over the twins’ bodies, tucking the soft material under their chins. One might mistake this act for something uncharacteristic of him, but the truth is simpler than that. He’s just making sure that his young master and his twin don’t catch a cold.

The young master makes a poor patient after all, so he’d like to avoid that.

The demon observes the twins. For the first time since he met the cowardly brat he now grudgingly calls Master, this might be the first time he understand his Master desperation. All of his trainings, his efforts, his drive—all of it for the slim chance of winning against his _Father_.

‘Sons of Satan,’ the demon mused, he has to swallow a bubbling laughs that threatened to escape his lips. What a joke, the grandest plot-twist to ever come into his long life. Here lie the youngest sons of the God of Gehenna. Both are covered in mortal flesh born of Assiah. One inherits the Divine Flame, while the other painfully human.

_‘Master Yukio, how come someone like you is the son of that Demon? Was it your mother that made you this way…’_

**Notes for the Chapter:**

> I always want to answer the exwires' question about their young teacher. Yukio is not phased with dressing as a woman for a mission, nor he seem a bit disturbed that there are two Shimas in the class. Konekomaru asked him what kind of life did he lead all this time... and the thought hits me hard.  
He's always the youngest in any exorcist gathering, I will not be surprised if some of his coworker tried to mess with him a little. There is a high chance that little cross-dressing is not Yukio's first time at disguising for a mission. His early career is going to be amusing. Not to mention, with Sebastian here, the probability of doing ridiculous thing for a mission skyrockets, he's a little schadenfreude like that. And Mephisto will not miss such amusing things unrecorded, that's why the album exist.
> 
> In other words, I'm going to slip hints or scenes about Yukio's early career. Please looking forward to those.
> 
> Don't expect speedy update, the third chapter is done but still needs to be proof-read.
> 
> Thanks for reading!

**Author's Note:**

> Hmm, since we're dealing with Kuroshitsuji, there will of course, some scenarios that sounds a bit like a shounen-ai, so if you don't like it please close the tab.
> 
> Also, the chapters has various length, so some might be shorter or longer than others.
> 
> thank you for reading so far!


End file.
